Method for insulation of coil of toroid transformers

A method for insulating at least one coil of a toroidal transformer, wherein one or more coils arranged on a core of the toroidal transformer are externally insulated, and wherein forming the outer electrical insulation of the one or more coils arranged on the iron core comprises:

• forming an opening in an electrically insulating thermoplastic cup receiving an iron core with a coil for leading through terminals of the coil;
• arranging the iron core with the coil in the cup such that the coil terminals are led out of the cup through the opening;
• covering the cup with the inserted iron core and coil with a plastic lid which engages the cup in a form-fitting manner;
• temporarily fixing the cup comprising the iron core and coil in an irrotatable manner;
• joining the cup and the lid by friction welding by pressing the lid placed on the cup against the cup and rotating it in this pressed state until the lid and the cup heat up and the material of the lid and the cup soften and become viscous due to friction;
• after softening of the materials of the lid and cup pressed together, stopping the rotation of the lid within not more than one second while maintaining the pressure of the lid and the cup;
• at maintained pressure joining the lid and the cup by their mixed material to form a continuous electrical insulation;
• and
• after cooling down and solidification of the materials of the joined lid and cup, removing the temporary fixing of the cup.